1. Field of the Invention
The present invention relates to a propylene polymer film. More particularly, it relates to a propylene polymer film having an excellent transparency, gloss, slipperiness, adhesiveness and adaptability to vacuum deposition, which is suitable for use as packaging material after vacuum deposition.
2. Description of Related Art
Many proposals have been made to improve the transparency and slipperiness of a propylene polymer film.
For example, Japanese Unexamined Patent Publication No. 63-105040 discloses a thermoplastic resin film containing inactive particles having a spherical shape and a pore volume of 0.1 to 3.0 milliliter per gram, and the film has a good transparency and handling property.
Japanese Examined Patent Publication No. 63-58170 discloses a polypropylene film containing a fine-powdered silica having an apparent specific gravity of 0.1 to 0.2 and a specific surface area of not more than 150 m.sup.2 /g, the film has a good transparency, slipperiness and antiblocking property.
Japanese Examined Patent Publication No. 61-36866 discloses a polymer film containing a fine-powdered aluminosilicate consisting of cubic shaped primary particles, and the film has a good slipperiness and antiblocking property.
U.S. Pat. No. 4,230,767 discloses a packaging material having an excellent seal packaging property, which comprises a base layer consisting of a stretched film made of a polymer composition comprising a propylene polymer and a surface layer consisting of a stretched film made of a polymeric mixture comprising a polymer blend, said polymer blend comprising a copolymer of ethylene and propylene and a copolymer of butene and any other polymerizable monomer. And it discloses that inorganic additives such as silica may be incorporated into the polymer composition as an anti-blocking agent and that there may be also used monoglycerides of fatty acid esters as an antistatic agent.
Japanese Unexamined Patent Publication No. 62-10141 discloses a process to make a porous film or sheet of a composition comprising a polyolefin resin, a filler, and triglyceride. And it discloses that inorganic substances such as silica can be used as a filler. But this porous film or sheet has a moisture permeability, and is preferably used for clothing material, medical supplies, a filter and so on.
Japanese Examined Patent Publication No. 60-57459 discloses a composition comprising a polyolefin resin and a glyceride of acylated 12-hydroxyoleic acid or 12-hydroxysrearic acid, which can be used to make a stretch film having a good softness.
Japanese Unexamined Patent Publication No. 53-54248 and Japanese Unexamined Patent Publication No. 54-36359 discloses a polyolefin resin film containing an glyceride, one acyl group of which has 2 to 6 carbon atoms and another acyl group of which has 8 to 22 carbon atoms, and this film has a good transparency.
European Patent Publication No. 0 210 750 A3 discloses a film-forming propylene polymer composition suitable for preparing a heat sealable polypropylene film and containing a propylene polymer and about 9 to about 14% by weight of a hard resin, and optionally a hydrocarbon wax, characterized in that the composition comprises about 86 to about 92% by weight of polypropylene, about 9 to about 14% by weight of a hard resin, and about 0.05 to about 0.8%, based on the weight of the composition, of a monoglyceride, a diglyceride, or a mixture of mono- and diglycerides, of behenic acid. The obtained film has improved antistatic properties.
European Patent Publication No. 0 242 055 A2 (Japanese Unexamined Patent Publication No. 62-215646), Japanese Unexamined Patent Publication No. 62-232448 and Japanese Unexamined Patent Publication No. 62-233248 discloses a propylene polymer film composed of a composition comprising a crystalline propylene polymer and a non-meltable crosslinked silicone resin powder having a means particle diameter of 0.5 to 7 microns, and the film has especially good transparency and exhibits a marked improvement in antiblocking property, bag opennability, slipperiness and appearance.
U.S. Pat. No. 4,725,466 discloses a non-sealable biaxially oriented multi-layer polypropylene film comprising a polypropylene homopolymer base layer and at least one covering layer, said covering layer comprising an aliphatic amine, a polydialkylsiloxane, a platelet-shaped inorganic pigment and a propylene homopolymer. The film has good anti-blocking and slip properties, good optical properties, good antistatic properties, and a high scratch resistance, and is used as a laminating film, an interleaving film or a metallizable film.
European Patent Publication No. 0 158 140 A3 discloses olefin polymer compositions containing silicone additives which can be extruded through relatively narrow die gaps at commercial extrusion rates to provide film material characterized by improved mechanical and optical properties.
And it is known that an organic fatty acid amide such as oleic acid amide, stearic acid amide or erucic acid amide is incorporated in a propylene polymer film to improve the slipperiness of the film.
The above-mentioned conventional propylene polymer films have a good transparency or a good slipperiness, but during the operation conducted after vacuum deposition on the film, defects or discharge traces are formed on the vacuum deposition layer by the discharge treatment, or small pinholes are formed or blocking is caused, resulting in peeling or wrinkling of the vacuum deposition layer. Namely, these films does not have a good adaptability to vacuum deposition.